1. Field of the Invention
The present invention generally relates to connectors, and more particularly to connectors for optical fibers which terminate in ferrules, and a system for manufacturing such connectors, which includes several parts common to each connector.
2. Description of the Prior Art
The use of optical fibers for high speed communication and data transmission via optical signals has become well established. There are already hundreds of thousands of miles of optical fiber in use today. It has, therefore, become imperative to provide compatible optical fiber connectors which may easily be coupled and uncoupled, and a substantial development effort has been directed toward designing such connectors. As used herein, the term "connector" means an article which allows connection, disconnection and reconnection of two optical fibers, as opposed to a "splice," which normally connotes a permanent connection between the fibers.
One of the earliest connector designs to become standardized is the ST fiber optic connector ("ST" is a trademark of American Telephone & Telegraph Co.); see U.S Pat. No. 4,634,214. This design incorporates a bayonet-style fastener. In its simplest form, this type of fastener includes a coupling having one or more outwardly extending projections or lugs, and a rotatable, female socket having a spiral slot therein for receiving the lugs. The coupling may include an integral mounting plate for affixing the connector to a connection module, or the coupling may comprise a double-ended receptacle which mates with two male connector plugs (one on each end of the fiber). A further improvement relates to the manner in which the female socket is rotated about the coupling. It was found that such rotation could result in undesirable grinding of the fiber end faces during the connection operation. To prevent such grinding, the connector body (ferrule) may be provided with means for aligning the ferrule with the connector receptacle. An improved version of the ST connector, shown in U.S. Pat. No. 4,812,009, provides a boot/cap extender which imparts strain relief to the connector assembly.
Another variation, illustrated in FIG. 1, comprises a "push-pull" connector 1 which is compatible with existing ST receptacles. The connector of FIG. 1 generally includes a ferrule 2 held by a ferrule collar 3 which in turn is secured within a connector body or backbone 4. A spring 5 surrounds a portion of the ferrule collar within body 4. A bushing 6 assists in the insertion of the optical fiber into collar 3. The entire assembly is further located in a slidable housing or shell 7 which serves to actuate the latch members s integrally formed with body 4. A crimp ring 9 is used to attach the strength members (Kevlar strands) of the fiber optic cable to body 4. A boot 10 is also provided for strain relief. See U.S. Pat. No. 5,101,463.
A similar push-pull fiber optic connector which is in wide use today is known as the "SC" connector, first manufactured by Nippon Telegraph and Telephone Co. An exemplary embodiment of this connector is shown in FIG. 2. A more detailed description may be found in "Japanese Industrial Standard JIS C 5973 for FO4-Type Optical Fiber Connectors," published by the Japanese Standards Association. This design also utilizes a double-ended receptacle, but both the receptacle and the plug 11 have a rectangular cross-section. Plug 11 has many components similar to those of ST push-pull connector 1, including a ferrule 12, collar 13, spring 14, crimp ring 15 and boot 16. While all of these components are different in construction from those of connector 1, the most notable difference is in the body 17, shell 18 and slidable housing 19 of SC connector 11. As with connector 1, pulling on the fiber optic cable attached to SC connector 11 will not disengage the elements, since the cable is directly attached to body 17 which is not directly coupled to ferrule collar 13.
Another popular connector style is the FC connector, which is similar to the ST connector in that it includes a circular shell, but does not provide for bayonet-style fastening. The first FC connector 20 (FC-PC2) is illustrated in FIG. 3. As with the other two connectors detailed, FC-PC2 connector 20 includes a ferrule 21, a ferrule collar 22, a spring 23, a backbone 24, a shell 25, a crimp ring 26, boot 27 and outer housing 28. This design is both pull-proof and side-pull resistant, but it has many parts and is relatively difficult to install. A later version of the FC connector (FC-PC1) has a low part count and is easily installed, but it is not pull-proof or side-pull resistant.
Due to the dissimilarities in the myriad connector styles, it has become difficult to service areas where several different styles are used; there are already several million of each of these types of connectors in use. Although each of the foregoing designs has unique advantages, the designs are totally incompatible. Each design requires different connector components, installation tools and procedures. Special adaptor kits may be necessary to achieve compatibility, and it is similarly more trouble to obtain jumpers which have different connector designs at each end. The multiplicity of styles also needlessly increases the overall cost of producing a variety of connector designs; there are a total of 24 different components in the three illustrated connectors. It would, therefore, be desirable and advantageous to devise a ferrule connector design which is easily adapted to existing connector styles, but has a simplified construction to facilitate assembly and reduce manufacturing costs, and yet is pull-proof and side-pull resistant.